One of my concerns with the 7950X3D under virtualization is how the system would handle the 7950X3D/7900X3D’s core parking mechanic. Basically, will Windows still attempt to park cores?
In one of the 7800X3D reviews (I think GN), it was pointed out that systems previously used with the 7950X3D would need a fresh Windows install because it would still attempt to park cores (parkour!) despite this mechanism not being needed on the 7800X3D. I am curious as to what exactly happens to a 7950X3D VM with half the core count.
It’s probably a good idea to stay as far away from chipset drivers in a VM as possible (also for non-V-cache CPUs) AFAIK those are responsible for the parking behaviour. So if you never install them, I don’t see how there could be an issue?
That said, I don’t have a 7950X3D to try it with. I can confirm however that the cache sizes of my 7950X are recognised correctly by Windows regardless of how I pin cores (1 CCD, 2 CCD’s, parts of CCD’s etc.)
There’s probably no way to be 100% sure without trying, if the AMD/Microsoft implementation is so buggy that it won’t recognise the difference between a 7950X3D and a 7800X3D. Though even then, one might be able to spoof the CPUs model to the hypervisor such that it is unaware of the exact model you have.
Ah, you’re right. I wasn’t sure how exactly the core parking mechanism worked, but chipset drivers makes sense. In my current system, I have it set up such that I can either boot into Windows via a Proxmox VM, or Windows baremetal (it’s installed on its own dedicated drive). This setup would probably not fly with the 3D v-cache parts, haha.
I am receiving my 7950X3D by end of this week, and my plan is to pass-through only the V-Cache cores. So, Windows will “see” an 7800X3D. Therefore, I won’t install chipset drivers (chipset actually is Q35 for VM) nor Gamebar.
My only concern is, how Linux will handle Core 0, since it is used by Kernel, even if you pin/isolate it.
does your board have the option to set the CCD for your host OS?
I got my new system yesterday, ASUS B650 Creator and 7950x, luckily had no problems, just transferred my config from the old system and was done.
On my CPU, the first CCD is a bit better, but apparently not all boards have the option to set the CCD to initialize the host system.
Did you change the cpu governor from the host?
My board has 3 options for the CCDs:
Frequency
Gaming
Auto
I set it to Frequency but haven’t notice any difference in the behavior. Even when running plain Linux, not the VM, it uses any available CPU core, not just the non-VCache ones.
Asus doesn’t follow 100% AMDs guidelines, so I am not sure how efficient this will be. At the moment, all the tests I have done point to correct utilization of cores and I haven’t even enable isolation.
These are my posts
And as I said, for now, I am not isolating, as I don’t have any issues. It turns out Linux scheduler does a great job. Also, Kernel 6.3 has even better scheduling for the V-cache processors, but haven’t try it, as it is beta and I am getting a white screen as soon as I login to KDE.
do you use 16 cores or 8 cores 16 threads? I get 97% single thread and exactly 50% multi-thread performance.
I use 4 cores per CCD, I also tried to use only one CCD, but the latency doesn’t get any better, currently I’m at about 60ns memory latency with Aida64.
Cinebench single thread always run way slower in my vm. Same as Geekbench 6. 85% is optimistic in my case.
You get 60ns latency inside vm? That is amazing. I am about 60ns on the bare metal.
Yes inside the VM.
You’re right, I hadn’t tested R23 single thread yet, single thread R23 It’s not quite there yet.
I am using an 40 bucks air cooler right now, it’s a good one, but when I got my AIO next week, I might get to 2000 points in single thread.
This is again a different configuration, it has the same 1% lows (Metro Exodus) as a single CCD configuration but better multi tread performance.
